The present invention relates to a stationary vane assembly in a turbo-machine, such as a gas turbine. More specifically, the present invention relates to an apparatus for locking a stationary vane to a turbo-machine cylinder.
A turbo-machine, such as a gas turbine, is typically comprised of several rows of stationary vanes, each of which is disposed immediately upstream from a row of rotating blades. Typically, a number of stationary vanes--for example, three--are formed into an assembly by a common outer shroud. The outer shroud is slidably supported on the turbine cylinder. The airfoils of the stationary vanes are exposed to the flow of working fluid and, therefore, must be restrained against the force applied to the vanes by the working fluid that tends to urge the vanes in the circumferential direction.
Traditionally, a Single pin or bolt attached to the cylinder engages the vane assembly outer shroud so as to prevent relative motion between the vane assembly and the cylinder in the circumferential direction. In the case of the first row of stationary vanes, such restraint was accomplished by a bolt that extended through a support rail formed at the outer shroud Leading edge and into the cylinder flange. In the case of downstream rows of vanes, a radially extending pin was inserted through the cylinder so that it entered a slot formed in a support rail located near the outer shroud trailing edge.
Unfortunately, this approach has not always been entirely adequate in restraining the vane. This is especially so in those cases in which the vanes are not grouped into assemblies, in which case each vane has its own short outer shroud. The use of a short outer shroud increases the tendency of the vane to rotate about the radial restraining pin, thereby causing wear on the outer shroud where it contacts the cylinder and misalignment of the vane with respect to the flow of the working fluid. In addition, the tendency for the vane to rotate about a single restraining pin causes a torque load to be imparted to the outer shroud. Over time, such torque load can result in undesirable creep deformation.
It is therefore desirable to provide a stationary vane assembly in which the vane is restrained with respect to the cylinder at two locations proximate the leading and trailing edges of the outer shroud.